Published: Jan 10, 2013 11:07 AM EST
Updated: Jan 10, 2013 11:20 AM EST

ST. PETERSBURG, Fla. (AP) - Police say a St. Petersburg teen shot himself in the head after telling friends he keeps one round out of the firing chamber to prevent an accidental discharge.
    
According to police 18-year-old Alexander Shaw was sitting on the back patio with friends Wednesday evening when he decided to demonstrate the gun's safety by holding it to his head and pulling the trigger. But the .38-caliber weapon discharged and the teen died at the scene.
    
Shaw's grandparents and uncle were home at the time. The incident is being investigated by homicide detectives and the medical examiner's office.
    
Police say Shaw's father was killed during a home invasion robbery on June 18. The teen was at the home and witnessed his father's death.

(Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)